1. Field of the Invention
This invention relates generally to power hand tools and, more specifically, to an Adaptive Dust Shield Device having Zero Standoff Capability.
2. Description of Related Art
Rotary grinders and similar rotary power tools are used extensively in industry. More specifically, angle type grinders/sanders having grinding discs or pads, are used for grinding concrete, fiberglass, wood, steel, removing asbestos, and body filler in automobile shops. Such grinders/sanders are also used for making boats and similar products. In use, these grinders create large quantities of dust that are both a fire hazard and a health hazard. Wood dust, for example, can be very explosive over a wide range of concentrations and is a known fire hazard. Hot metal grindings are particularly dangerous as fire starters. Both wood dust and metal filings, as well as asbestos particles, fiberglass and body filler particles, create known health hazards to users of the grinders and to others in the immediate environment. It is known that concrete dust, as typically generated in great quantities from grinding concrete, is a principal cause of pulmonary silicosis.
Grinder discs and pads often rotate in excess of 7,000 revolutions per minute (RPM). Grinding pads that use a sponge type backing material create a hazard where parts or particles from the backing material break off and are shot from the rotating disc tangently at a high rate of speed. It is often necessary to use a rotary grinder to grind into corners or against surfaces that have side edges that can cause particles of the foam backing material to break off from the high speed rotating disc and hit the operator or other persons or equipment in the immediate area.
A dust shield described in U.S. Pat. No. 5,125,190 approached this problem and solved it to some extent. It has an upstanding attachment collar [reference character 16 of U.S. Pat. No. 5,125,190] which had a diameter chosen to fit onto the bearing housing [reference character 38 of U.S. Pat. No. 5,125,190] of a variety of different grinders. Grinders from varying manufacturers have different diameters for their respective bearing housing. Typical diameters of bearing housings range from one and one-half inch to three inches, and therefore a one-size attachment collar on the dust shield would not accommodate the varying bearing housings. Consequently, several different models of the dust shield, each having different collar diameters, had to be manufactured for the various make grinders or requires an adapted. This, of course, increases manufacturing costs and adds to inventory of a supplier and end-user since most end-users have more than one grinder and more than one make.
Without the adapter, the retailer generally must carry up to 40 SKUs (stock keeping units) to cover all the grinders made. With the adapter, the retailer will need only 6 stocking units, one for each of the major disc diameters of 2, 3, 5, 6, 7 and 8 inches. Space in a retail store is very valuable, and therefore the reduction of SKUs adds value to the adapter because it can reduce the amount of space needed to provide a line of dust shields that can fit all grinders.
Additionally, the grinding surface of different brands of grinders with different grinding disks varies in distance from the bearing housing of the grinder where the dust shield is attached. The dust shield of U.S. Pat. No. 5,125,190 was not readily capable of a distance adjustment to bring the grinding surface down to where it can be of effective use or, in some cases, any use at all. The collar (reference character 16 of U.S. Pat. No. 5,125,190) had to be individually and carefully sanded down such that its lower edge (reference character 35 of U.S. Pat. No. 5,125,190) was accordingly raised thereby bringing the grinding surface out to point of use. Cutting the skirt, improper sanding, or improper measurements would in essence ruin the dust shield and be a waste of time and money.
Additionally, the plastics formulation used in the manufacture of the adaptive dust shield is such that, if cutting the adaptive dust shield is necessary, it can easily be cut with ordinary household scissors without ruining the adaptive dust shield in its entirety. The formulation provides for greater flexibility, thereby eliminating much of the need to make distance adjustments of the fitting ring into and away from the bearing housing and into and away on the upstanding fingers.
FIG. 1 is an exploded perspective view of the adaptive dust shield device of U.S. Pat. No. 8,282,447 100 and a conventional angle grinder 60. The dust shield 100 attaches to the bearing housing 68 of the grinder 60. In order to accommodate the widest variety of grinder 60 models, the dust shield 100 may be used with a split fitting ring 110, that slips over the bearing housing 68 before the ring formed from the upstanding fingers 178 are slipped thereover. The securing fastener 88 is then attached to encircle the upstanding fingers 178, fitting ring 110, and bearing housing 68, and tightened around the combination. This securely holds the dust shield device 100 to the grinder. An external hose 82 from the user's vacuum system attaches to the exit opening 86 of the exhaust port 80. The air vents 75 and angled slots 184 allow air to flow in to the internal chamber under the cover 170 in order to create sufficient airflow through the system and into the external vacuum system through the exhaust port 80. It also prevents the creation of too much suction on the bottom of the cover 170, which tends to make the cover want to stick to the surface that the user is working above.
Through experience with the dust shield 100, it has been noticed that in certain circumstances, it is necessary to cut, grind or polish in “zero clearance” or “zero standoff” conditions. An example of a zero clearance condition would be where the user needs to grind a floor up to where it meets a wall or other vertical obstruction. In such a case, the outer periphery of the grinding wheel needs to be exposed, because otherwise the dust shield 100 would prevent the user from reaching all the way to the wall/vertical obstruction. Historically, the user would simply remove the dust shield 100 from the grinder while doing any zero clearance sections. As should be apparent, removal of the dust shield for any reason during operation is dangerous and unhealthy.
What is needed, then, is an adaptive dust shield for angle grinders that can accommodate grinding in zero clearance situations without the need to remove the dust shield from the grinder.